Plant Cells and Tissues

Study Notes

Plant tissues are groups of cells that work together for structure and function.
Tissues form systems in plants.
There are three tissue systems: ground, vascular, and dermal.

Parenchyma cells:
- Unspecialized plant cells.
- Thin walls.
- May contain chlorophyll.
- Loosely packed.
- Functions: photosynthesis, storage, secretion.
Collenchyma cells:
- Living plant cells.
- Unevenly thickened primary walls.
- Provide support in soft, non-woody plant parts.
Sclerenchyma cells:
- Plant cells with extremely thick walls, providing strength and support to the plant body.
- Two types:
  - Sclereids: found in shells of nuts, stones of fruits, pears.
  - Fibers: found in wood, inner bark, and leaf ribs.

Xylem:
- Transports water and dissolved minerals throughout the plant.
- Tracheids and vessel elements conduct water and minerals.
- Parenchyma cells are for storage.
- Fibers provide support.
Phloem:
- Transports food (sugars) throughout the plant body.
- Sieve tube elements are long, thin cells stacked end-to-end forming sieve tubes.
- Sieve plates are end walls with holes for cytoplasm to connect cells.
- Companion cells are adjacent to sieve tube elements; assist in functions of sieve tube elements.

Epidermis:
- Outermost layer (usually one cell thick).
- Covers the plant body.
- Cuticle is secreted on stems and leaves to reduce water loss.
- Stomata facilitate carbon dioxide diffusion during photosynthesis.

Apical meristems:
- Located at tips of stems and roots.
- Produce primary tissues (responsible for plant's primary growth — increasing length).
Lateral meristems:
- Located on the side of the vascular plant.
- Vascular cambium and cork cambium give rise to secondary tissues (responsible for secondary growth, widening the plant).